Field of the Invention
The present invention relates to a wireless communication, and more particularly, to a method and apparatus for ranging in a wireless communication system.
Related Art
The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
There is ongoing development on the IEEE 802.16p standard optimized for machine-to-machine (M2M) communication based on the IEEE 802.16e standard and the IEEE 802.16m standard. The M2M communication can be defined as an information exchange performed between a subscriber station and a server or between subscriber stations in a core network without any human interaction. In the IEEE 802.16p standard, there is an ongoing discussion on enhancement of medium access control (MAC) of the IEEE 802.16 standard and a minimum change of an orthogonal frequency division multiple access (OFDMA) physical layer (PHY) in licensed bands. Due to the discussion on the IEEE 802.16p standard, a wide area wireless coverage is required in the licensed band, and a scope of applying automated M2M communication can be increased for an observation and control purpose.
When accessing a network, requirements demanded by many M2M applications are significantly different from requirements for human-initiated or human-controlled network access. The M2M application can include vehicular telematics, healthcare monitoring of bio-sensors, remote maintenance and control, smart metering, an automated service of a consumer device, etc. The requirements of the M2M application can include very lower power consumption, larger numbers of devices, short burst transmission, device tampering detection and reporting, improved device authentication, etc.
Ranging implies a process for maintaining quality of radio frequency (RF) communication between the UE and the BS. According to the ranging, a timing offset, a frequency offset, and a power adjustment value can be accurately obtained, and transmission of the UE can be aligned with the BS. A plurality of M2M devices can perform contention-based ranging with each other. The plurality of M2M devices may belong to an M2M group. M2M devices belonging to the same M2M group share a criterion of the same M2M service application and/or the same M2M user.
Meanwhile, data which an M2M device needs to transmit is not frequently generated and there is a high possibility that a time required to transmit or receive the data will also be very short. As a result, when a section in which the M2M device transmits or receives the data is excluded, it is anticipated that the M2M device will operated in an idle mode during most time. However, when a paging message is transmitted to the M2M device from a network in order to transmit data to a lot of M2M devices that belong to the idle mode, the plurality of M2M devices that receives the paging message may simultaneously perform ranging in order to receive the data. It is assumed that the M2M device can receive the data only in a connected state. Further, even when it is anticipated that the data is transmitted to an M2M server from a plurality of M2M devices that belongs to a specific M2M group simultaneously, the plurality of M2M devices may perform ranging simultaneously.
Therefore, dedicated ranging channel and resources for the M2M device need to be configured in order to prevent a collision and minimize an influence on existing human type communication (HTC) devices when the plurality of M2M devices attempts ranging.